iommu/vt-d: Don't switch off swiotlb if bounce page is used

The bounce page implementation depends on swiotlb. Hence, don't
switch off swiotlb if the system has untrusted devices or could
potentially be hot-added with any untrusted devices.

Cc: Ashok Raj <ashok.raj@intel.com>
Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>
Cc: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

2 files changed, 18 insertions, 15 deletions

diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index e15cdcd8cb3c..a4ddeade8ac4 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -182,6 +182,7 @@ config INTEL_IOMMU
         select IOMMU_IOVA
         select NEED_DMA_MAP_STATE
         select DMAR_TABLE
+        select SWIOTLB
         help
           DMA remapping (DMAR) devices support enables independent address
           translations for Direct Memory Access (DMA) from devices.
diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index ce6baabc9dcc..0af7b4669264 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -4547,22 +4547,20 @@ const struct attribute_group *intel_iommu_groups[] = {
         NULL,
 };
 
-static int __init platform_optin_force_iommu(void)
+static inline bool has_untrusted_dev(void)
 {
         struct pci_dev *pdev = NULL;
-        bool has_untrusted_dev = false;
 
-        if (!dmar_platform_optin() || no_platform_optin)
-                return 0;
+        for_each_pci_dev(pdev)
+                if (pdev->untrusted)
+                        return true;
 
-        for_each_pci_dev(pdev) {
-                if (pdev->untrusted) {
-                        has_untrusted_dev = true;
-                        break;
-                }
-        }
+        return false;
+}
 
-        if (!has_untrusted_dev)
+static int __init platform_optin_force_iommu(void)
+{
+        if (!dmar_platform_optin() || no_platform_optin || !has_untrusted_dev())
                 return 0;
 
         if (no_iommu || dmar_disabled)
@@ -4576,9 +4574,6 @@ static int __init platform_optin_force_iommu(void)
                 iommu_identity_mapping |= IDENTMAP_ALL;
 
         dmar_disabled = 0;
-#if defined(CONFIG_X86) && defined(CONFIG_SWIOTLB)
-        swiotlb = 0;
-#endif
         no_iommu = 0;
 
         return 1;
@@ -4718,7 +4713,14 @@ int __init intel_iommu_init(void)
         up_write(&dmar_global_lock);
 
 #if defined(CONFIG_X86) && defined(CONFIG_SWIOTLB)
-        swiotlb = 0;
+        /*
+         * If the system has no untrusted device or the user has decided
+         * to disable the bounce page mechanisms, we don't need swiotlb.
+         * Mark this and the pre-allocated bounce pages will be released
+         * later.
+         */
+        if (!has_untrusted_dev() || intel_no_bounce)
+                swiotlb = 0;
 #endif
         dma_ops = &intel_dma_ops;